Coloration is an important characteristic of commercially grown grapes. Grapes with uniform and desirable color can command premium prices in the market. In addition, color development is an important indication of grape maturation and impacts the harvest time. It is desirable for grape clusters in a field to mature at the same time in order to eliminate harvesting immature fruit with the mature fruit. Thus, pre-harvest treatments of grapes that promote uniform and early development of grape color have significant commercial value.
Currently, there are two products commercially available for enhancing grape coloration. One of the products, Ethrel® (available from and a registered trademark of Bayer) contains ethephon. Ethephon (2-chloroethylphosphonic acid) is an ethylene precursor which is rapidly converted into ethylene in plants. While ethephon is effective at enhancing fruit coloration, it is also difficult to apply to the grapes, requires high application rates, and does not provide consistent results. In some areas, there is also concern about the safety of ethephon use.
The other commercially available product, ProTone® (available from and a registered trademark of Valent BioSciences Corporation) contains (S)-abscisic acid. (S)-abscisic acid is a plant growth regulator that promotes plant or fruit maturity and color development by directly augmenting anthocyanin synthesis. While (S)-abscisic acid (“S-ABA”) is very effective at enhancing fruit coloration, relatively high concentrations must be used in order to achieve desired results.
Accordingly, there is a need for new methods for enhancing grape coloration in order to produce highly marketable grapes. The new methods should be cost-effective for the growers and produce consistent and reliable coloration results.